Bone anchors made of polymeric materials such as polyether ether ketone (“PEEK”) are interesting as they are fully compatible with standard imaging techniques like X-Rays, computed tomography (“CT”) or Magnetic Resonance Imaging (“MRI”). In particular no artifact is generated when using CT or MRI that would disturb diagnostics. In case of X-rays, PEEK anchors are not visible. PEEK is, however, known to be poorly osseointegrative and therefore there is a need to overcome this disadvantage.
The surface of polymers, such as polymers in the PAEK family, is often not compatible with soft or hard tissues like bones. Implants made of these materials may poorly integrate and finally dysfunction. The risk of migration or loosening of the polymer-tissue interface may be a significant consideration, in a polymer-based device, and therefore the polymer surface is often modified to improve the osseointegration. One method to achieve this modification is to spray a thick coating of a titanium oxide powder, with for example vacuum plasma spray (“VPS”), as the bioactivity of titanium oxide is much higher than the one of polymers such as PAEK or PEEK. However, these techniques (such as VPS) may not ensure a good anchoring, between the titanium oxide surface and tissue, and the high process temperature may contribute to the deterioration of the properties of the polymer. In addition, application of a thick VPS coating on complex geometries may be challenging due to the shadowing effect of the spray and the relative large thickness (e.g. 200 μm) that may leverage out any fine structure of the implant surface would have. Furthermore the so-called “splash” structure of plasma spray coatings may not exhibit a suitable pore structure as the pores are fine and elongated and the overall porosity limited.
Additionally, titanium layers made by physical vapor deposition (“PVD”) may be dense and thin, for example approximately 1 micrometer or less, and thus, in some circumstances, titanium PVD thin layers may not be satisfactory for implants.
Embodiments of the present invention overcome one or more of these challenges.